AwsS3 Multipart Uploads #513
This is a modification of AwsS3 adapter to allow multipart uploads when files are bigger than a certain size.
Size limits / part size are passed as options to the adapter and set to defaults, respectively 5Go and
Limitations : won't work with string content, you have to pass a resource handle otherwise write() will return false. We may use InMemoryStream to bypass this limitation ?
PHP7.1 fails on docker image, not sure why. May need some help on this.